An upcoming mod turns Alien Swarm into a co-op first-person shooter.
While Aliens: Colonial Marines' rushed qualities might have crushed the dreams of many a xeno fan, hope remains, for there is a light on the horizon. While Valve's entirely free Alien Swarm might have both aliens and swarms, its top-down perspective doesn't create the same immersive experience that a first-person view might. To remedy that comes Alien Swarm FP, a mod that adds just that, turning it into a sci-fi Left 4 Dead that just might wash the taste of Colonial Marines out of the mouths of the many unfortunate people who purchased it.
While it's currently possible to enable a first-person perspective via console commands, the Alien Swarm FP mod fleshes it out. This means first-person weapons, ceilings, jumping, and everything else that got ironed out of the top-down game. Aside from reworking the entire campaign, additional campaigns and Oculus Rift support are planned, although that might be overly ambitious. While it's not yet released, it's currently up on Steam Greenlight.
Alien Swarm started out life as an Unreal Tournament mod until it got absorbed into Valve. Using their newfound resources, the original mod team quietly toiled away on an upgraded Source Engine version, which was released entirely free in 2010. Valve also released an SDK, which allows modders to edit the game however they see fit. Considering its history, releasing a free game replete with modding tools seems like a great way to grow the next generation of game developers/Valve employees.